Airplane strut



p 26, 1939-- E. w. CLEVELAND 2,174,312

AIRPLANE STRUT Filed Oct. 3, 19:55

INVENTOR.

ATTORNEYJI Patented Sept. 26, 1939 UNITED STATES AIRPLANE swam Ephraim W. Cleveland,

Berea, Ohio, assignor to The Cleveland Pneumatic Tool Company, Cleveland, Ohio, a corporation of Ohio Application October 3, 1935, Serial No. 43,377

10 Claims.

This invention relates to improvements in airplane struts, and relates to a strut in which the shock of impact upon landing is taken first upon liquid, that is by flow through a metering opening, and then upon compressed air, the shocks of taxying being absorbed principally by compressed air. g I

One of the objects of the invention is to provide a construction 01' this character which shall be simple and compact, providing a strut of consider'able length when the airplane is in flight and one of diminished length when it is on the ground.

Other objects and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawing, in which Fig. 1 is an elevational view, partly in central ,the strut fully extended, as it would be when theairplane was in flight and about to land.

The strut illustrated herein comprises a pair of telescoping cylinders l0 and II which are closed at or near their ends, and are adapted to be attached at their outer endsto the elements whose relative movements are to be cushioned, these elements in most cases being the wings or fuselage of an airplane on one hand and the running gear on the other. The cylinder III may include a portion Illa of reduced diameter at its upper end, the two portions being preferably connected by a weld l2. At the junction of these two parts there is an annular shoulder I3. A .tube It arranged axially of the strut depends from the head of the inner cylinder, where it communicates with a hollow fitting I! closed by a cap I 6. when the strut is to be charged-with oil or other liquid. the ,latter is introduced through fitting l5 and the tube ll. When the liquid being poured into the strut rises to the level of the bottom of tube It the escape of air through the tube is cut off, and; hence the quantity of liquid which may be placed in the strut is accurately determined.

The lower end of cylinder III is threaded to receive a ring I! which has a good sliding fit with the inner wall of cylinder l I. This ring also serves to clamp a partition plate It to the end of the cylinder III. This plate is provided with a centralmetering opening I 9, and in addition may have one or more smaller openings 20.

A metering pin 2| cooperates with the metering opening it, being preferably tapered toward its upper end, and being threaded at its lower extremity for mounting in the head 22 of the cylinder l I. As will be apparent, the partition plate l8 divides the space surrounded by the two cylinders i0 and it into two compartments 23 and II. On movements of compression from the extended position of the strut illustrated in Fig. 2 toward. the position illustrated in Fig. 1, liquid from the lower compartment 2] is forced through the metering opening I! and through the restricted opening or openings 20,. if any of the latter are used, the restricted passages through the partition delaying the flow of liquid sufiiciently to pre- 1 vent a heavy shock to the airplane. Liquid metering apparatus of this kind and for this purpose is well known in the art.

On the threaded upper end of the cylinder section Ida there is mounted an auxiliary annular a head 25, to which is welded a third cylinder 26 that surrounds the telescoping cylinders Ill and I I and extends downwardly substantially the same distance as cylinder l0. Near its lower end this cylinder is internally enlarged somewhat to re- 85 ceive a packing 21 and a packing gland nut or sleeve 28, these parts being of any suitable character, and the sleeve 28 being locked in adjusted position by appropriate means, such as a spring ring 29 with an inturned end 30 projecting into a slot II in the sleeve.

Near the upper end of the cylinder ii there is an external ring 32 which has a close sliding fit on the wall of cylinder 26. This ring forms the upper closure for an annular chamber 33 between 35 the cylinders II and 26, the packing 21 constituting the lower closure for the same. This annular chamber of course varies in size with the movements of the strut. It is in communication with an inner annular chamber 3| through one or 40 more small ports 35 in the cylinder II. The latter cylinder carries an annular shoulder 3' which limits the expansion of the strut by its engagement with the packing 21, as shown in Fig. 2.

Between the cylinder section Illa and the outer .45 cylinder 26 there is an annular air chamber 31. In this chamber there is a floating annular piston 38 having an integral bottom ring 39 and'a separable top ring 40, the latter being L-shaped in cross section so as to provide an .oil receptacle. Between the rings 39 and 40 and on either side of the main portion oi the piston are packings H and 42, by means of which the piston is sealed against the cylinder section Illa as well as against the cylinder 26. Annular flanges 43 and 44 ex- M 1 taper of pin tend downwardly irom the ring 88 in order to retain floating rings 45 and 48 of metal, above which are positioned rings 4! and 48 of soft rubber.

On the upper extremity of cylinder H there is an annular extension 49 that is adapted to engage the ring 46 when the cylinder it is raised sufficiently, and by this means upward motion may be imparted to the annular piston 38. The rubber ring 48 forms a cushion which yields sufllciently to deaden noise and prevent damage to the parts when. this engagement takes place sud= denly. When the piston is forced downwardly by the compressed air in chamber 37, causing ring to to engage shoulder It, the rubber ring 4'l yields to cushion that engagement and reduce noise.

Fla. 2 represents the strut in fully extended position, with the floating piston 38 down. against the shoulder ll]. This is the position which the parts occupy when the airplane is in flight, er;- cept where some means is used for retracting the running gear in order to reduce wind resistance.

In the latter case the cylinder ill is drawn up to the position shown in l by any suitable connections, where it is held until the pilot to moire a landing, when it is lowered to the peel tion of Fig.

When a landing is made the impact of the run ning gear on the ground forces the cylinder l l upwardly relative to the other elements of the strut, the liquid in the chamber then being metered through the constricted passages l9 and it into the chamber 23. The l9, due to the El gradually decreases size as the cylinder rises. This metering oi liquid absorbs a considerable portion. or the force of the li pact. Sometime before the cylinder it reaches the top of its stroke the extension to on its upper end engages annular piston and starts up ward against the compressed air in chamber The air then the metering oi liquid cushioning the balance at the impact stroke. its the plane tastes over the ground, shocks are absorbed on the soft cushion, assisted by the metering of hauls through the openings 39 and to, while the rebound strokes are checked by the suction created beneath plate 518, one suction being; relieved gradually by the metering of oil downwardly through the constricted openings in the plate.

Variations from the described structure may be employed. Accordingly ll desire it to be clerstoocl that the scope of the invention is to regarded as defined exclusively by the appended claims rather than by the foregoing description or the accompanying illustration.

Having thus described my invention, I claim:

14in a shoal: absorbing strut, two relatively movable members adapted to be attached to the elements whose movements are to be cushioned, a compartment in each of said members with a partition separating the compartments, said partition having a liquid metering opening therethrough, a third compartment containing air under pressure, a piston in said third compartment, and means made effective by the latter portion of the compression stroke only for causing one 05 said members to engage and move said piston in its compartment for reducing the volume of said third compartment and correspondingly checking the compression of the strut.

2. In a shock absorbing strut, two telescoping cylinders closed at their outer ends, a partition dividing the space within the cylinders into two compartments, said partition having a liquid metering opening therethrough, a third cylinder surrounding one of said telescoping cylinders, an annular piston interposed between said third cylinder and said last named telescoping cylinder, said piston forming one wall of an air chamber, and means made effective by the latter portion of the compression stroke for moving said piston to reduce the volume of said air chamber,

In a shock absorbing strut for airplanes, means for metering liquid in opposition to the impact stroke on landing, comprising two tele scoping cylinders having their inner ends com. municatlng through a liquid metering opening, and secondary shock absorbing means comprising an annular air chamber suriounding one of said cylinders, an annular piston in said chamber, and means made effective only after the cylinders have been telescoped to a predetermined extent for ausing the to respond to further relative movements of the cylinders.

In a shock absorbing strut for airplanes, means for metering liquid in opposition to the impact stroke on landing, comprising two telescoping cylinders with their inner ends communicathie through a liquid. metering opening, a secondary shock absorbing means comprising an air chamber concentrically arranged with respect to said cylinders, a piston floating said. chamber, the outer end of one of cy tiers having a projecting portion adapted to e gage said piston only after strut has coan-- pressed to a predetermined extent.

5. In a shock absorbing strut tor means for metering linuld in opposition to the impact stroke on lending, comprising two tele scoping cylinders with their inner corn nounlcating through a liquid metering opening, a secondary shock absorbing means comprising an annular air chamber surrounding the exposed portion of the inner cylinder, and an annular piston floating in said chamber, the outer one of said cylinders having an extension to engage said piston only after the strut been compressed to a predetermined extent.

6. An airplane shock absorbing strut comprising telescopic casings, '2, metering pin carried. by one of the casings, an orificecl pistol-1 by other casing for cooperation with the pin, a compressed air chamber in one oi the casings, a piston movable in the air chamber for intposlng pressure on air contained therein adapted. to seat on the other casing only after the liquid has been metered.

l An airplane shock absorbing strut comprisins telescopic casings, a metering pin carried by one of the casings, an orlflced piston carried by the other casing for cooperation with the pin,

an annular piston adapted to seat on the rod 05 the piston when the strut is in extended posltion and toseat on the casing carrying the metering pin when the strut is in collapsed position, and a chamber forward of the annular piston adapted to contain air under pressure.

8. An airplane shock absorbing strut comprislug telescopic casings, a metering pin carried by one of the casings, an inner casing having a shoulder intermediate its length, a piston on the inner casing having an orifice for cooperation with the pin, an annular piston reciprocable on the inner casing adapted to seat on the shoulder when the strut is extended and on the casing carrying the metering pin when the strut is collamed, and a chamber forward of the annular piston adapted to contain air under pressure.

9. An airplane shock absorbing strut comprising telescopic casings closed at their outer ends. a metering pin carried by one of the casings, an inner casing carried by the other casing, -a shoulder on the inner casing intermediate its length, a piston on the inner casing having an oriflce for cooperation with the pin, an annular piston reciprocable between the inner casing and the outer casing adapted to seat on the shoulder when the strut is extended and on the casing carrying the metering pin when the strut is collapsed, and a chamber forward of the piston adapted to contain air under pressure.

10. An airplane shock absorbing strut comprising telescopic casings closed at their outer ends, a metering pin carried by one oi the casings, an inner casing carried by the other casing, a shoulder on the inner casing, an oriflced piston on the inner casing for cooperation with the pin, an annular piston reciprocable between the inner casing and the casing supporting the inner casing, an oil receptacle carried by the annular piston, said annular piston adapted to seat on the shoulder when the strut is extended and on the casing carrying the metering pin when the strut is collapsed, and a chamber forward of the annular piston adapted to contain air under 

